Temperature-controlled apparatus



Jam. 1923-2. 1,481,021

L. MARSHALL Filed Feb 2, 1 .22

Patented Jan. 15, 1924.

PATENT orr ca.

LAURENCE K. MARSHALL, OF WEST SOMEEVILLE, MASSACHUSETTS, ASSIGNOR TOSPENCER THERMOSTAT COMPANY, OF CAMBRIDGE, MASSACHUSETTS, A CORPORA- TIONOF MASSACHUSETTS.

TEMPERATURE-CONTROLLED APPARATUS.

Application filed February 14, 1922. Serial No. 536,478.

To all whom it may concern:

Be it known that I, LAURENCE K. MAR- SHALL, a citizen of the UnitedStates, residin at West Somerville, in the county of Midfiesex and Stateof Massachusetts, have invented certain new and useful Improvements inTemperature-Controlled Apparatus; and I do hereby declare the followingto be a. full, clear, and exact description of the invention, such aswill enable others skilled in the art to which it appertains to make anduse the same.

The present invention relates to temperature controlled apparatus andmore particularly to thermostats embodying a plurality of metallicconstituents having different coefiicients of expansion.

Bimetallic strips have been employed as thermostatic controls andoperate satisfactorily over a limited range of temperatures. Thesethermostats as heretofore developed, however, have not functionedefficiently where the range of temperature to which the thermostat wassubjected exceeded a comparatively narrow range.

The object of the present invention it to produce a thermostatic controlwhich may be ub'ected to a wide range of temperatures wi out detrimentaleffect and which opcrates efficiently at comparatively hightemperatures.

- With this object in view one feature of the present inventioncontemplates the provision of a thermostatic control consisting of aplurality of metals each having variable coefiicients of expansion sochosen with respect to one another that the greatest rate of defiectionon account of temperature changes 'gnccurs within the working range atwhich 40 thethermostat is to act. Above and below thisworking range, therates of deflection are less and may preferably be low at normal roomtemperatures to which the thermostat is subjected when not in operation.

in connection with the control of electric current applied to variousinstrumentalities, such as flatirons, for exam' le. In apparatus of thissort, it is desirab e to have a temperature control which functions at atemperature range from 200 C. to 350 C. a proximately. In the resentinvention t e 5 thermostat is designed in such a manner that Such athermostat is particularly useful the greatest rate of deflection occursat this range. On the other hand, when the fiat- 1ron cools down andremains at room temperatures the deflection rate, due to the differentcoefiicients of expansion, is materially less and is such thatsubstantially internal stresses are not imposed upon the thermostaticcou 1e.

A still urther feature of the present invention contemplates abimetallic strip consistmg of two alloys of different metals, each alloyhaving a variable coefficient of expansion, the difference between themethcients of expansion of the two alloys being greatest throughout aran e of comparatively high temperatures and materially less fortemperatures above and below the working range. This constructionproduces a thermostatic couple having its greatest sensitivity at acomparatively high temperature and least sensitivity at temperaturesoutside of the desired range.

The accompanying drawing illustrates diagrammatically the temperatureand expansion curves of certain alloys which may be advantageouslcombined to produce a thermostatic couple according to the presentinvention;

The present invention ma be embodied with s ecial utility in a termostatically control ed electric flatiron in which the thermostaticmember employed for controlling the tem rture of the flatiron comprisesa bimetallic sheet or strip so designed that when predetermined limitsof temperature are reached the strip abruptly changes its shape, due tothe internal stresses set up therein, this abrupt change of shape beingutilized to control the flow of heatin current. In apparatus of thistype it 15 desirable that the control shall function over a workingrange varyingI between 200 C. and 350 C. ap roximate y. Althou h thecontrol should ave the greatest de ection rate at this approximateworking range, nevertheless when the flatiron is not in use the controlis at room temperature and it must accordingly be capable ofwithstanding the wide range of temperature between room temepratures andthe working range without creatin internal stresses suflicient to exceedthe limits of elasticity of the metals and cause permanent deflection.Furthermore the metals comprising the thermo stat must be of such anature that they dot not lose their temper when the control is heated tothe comparatively high temperatures within which the working range lies.

As illustrations of certain s ecific forms of thermostatic members emboying the desired pro rties may be mentioned the combination in abimetallic strip of pure nickel and a nickel steel alloy having forty toforty-five per cent nickel. Upon referring to the accompanying drawingit will be observed that the coefiicients of expansion of these twomaterials are variable and differ the most throughout a temperaturerange of 200 C. to 350 0. approximately. Above and below thistemperature range, the coefiicients of expansion of the two materialsare less and at temperatures between er nickel; a combination of nickelsteel havi 400 C. and 500 C. the coefiicients of expansion arepracticall the same. As examples of other combinations which may besatisfactorily employed for high temperature thermostats ma be mentioneda combination of invar, w ich is a nickel steel having thirty-five percent nickel approximately, and a nickel steel having forty centfoxy-five per cent nickel approximately an in cable nickel havingninety-six per cent nickel and four per cent man anese approximately; acombination of onel metal consisting of cop r and about two thirdsnickel and a nic el steel having forty to fift per cent nickel; and acombination of niclze silver and nickel steel having forty to fifty percent nickel. In addition to the metals and alloys specificallyenumerated, certain other metals and the alloys of these metals may wellbe employed in combination, depending upon the character of use to whichthe thermostat is to be put and the working range over which itisdesired that the thermostat shall operate.

I claim 1. A high temperature thermostatic control composed ofacombination of metallic constituents, said constituents having variablecoefiicients of expansion withthe greatest difi'erences in expansionover aworking temperature range substantially above room temperaturesand less difierences in expansion at temperatures outside said range.

2. A high temperature thermostatlc control composed of a plurality ofdifierent metallic constituents, said constituents being so related withres ct to one another that the rate of deflection of the thermostaticmember on account of .tem rature changes between 200 C. and 350approximately is large and the rate of deflection, on account oftemperature changes above 400 C. is substantially less. y

3. A heat-responsive device comprising metallic elements havingcoeflicients of expansion t coefiicients of expansion which difi'er atleast two to one within a range of temperatures above 250 C.

4. A heat-responsive device comprising metallic elements havingcoefiicients of ex.- pansion which differ at least two to one within therange 200 to 350 (3., the element having the lower coefficientcontaining a minimum of 40 per cent nickel.

5. A heat-responsive device comprising metallic elements whosecoeflicients of expansion have a maximum difference within thetemperature range of 200 to 350 C. approximately.

6. A heat-responsive device comprising metallic elements having widelydlfierent coeflicients of expansion at temperatures above 200 (3., theelement having the higher coeflicient at such temperatures containingnickel.

7. A heat-responsive device comprising metallic elements having widelydifierent coeflicients of expansion at temperatures above 250 C., bothelements containing nickel.

8. .A heat-responsive device comprising metallic elements having widelydifierent coefficients of expansion at. temperatures above 200 0., bothelements containing nickel and the nickel content of the element havingthe lower coeflicient at such temperatures being at least approximately35 per cent.

9. A heat-responsive device comprising metallic elements havinghrwidelydiiferent coefficients of expansion oughout a ran e of temperaturesabove 200 C, the above e ement having the higher coefiicient within saidrange having a coeflicient approximately that of nickel and the otherelement having a higher coefiicientthan invar at room temperatures. a

10. A heat-responsive device comprising metallic elements havingilwidely different roughout a range of temperatures above 200 (1., theelement having the lower coeiiicient within said range havin acoeificient of the order of that of a nickel steel containingapproximately 42% nickel.

11. A heat-responsive device comprising metallic elements havincoeflicients of expansion t roughout a ran of temperatures above 250 0.within Whi range one element has a coefliclent at least widely differentapproximately ashigh as that of nickel and the other element imatelythat of steel containing 42 per cent nickel.

12. A heat-responsive device comprising metallic elements one of whichis at least approximately other of which is an alloy containing atleastapproximately forty per cent nickel.

13. heat-responsive device comprising has a coefiicient approxtwo-thirdsnickel and the metallic elements one of which is at least approximatelytwo-thirds nickel and the other of which is a steel allo containingapproximately forty to fortyve per cent nickel.

14. A heat-responsive device comprising metallic elements one of whichis at least approximately two-thirds nickel and the other of which is asteel alloy containing approximately forty-two er cent nickel.

15. A heat-responsive (levice comprising metallic elements one of whichis Monel metal and the other of which is an alloy containing at leastapproximately forty per cent nickel.

16. A heat-responsive device comprisin metallic elements one of which isMone metal and the other of which is a steel alloy containingapproximately forty to forty- 20 five per cent nickel.

17. A heat-responsive device comprisin metallic elements one of which isMonel metal and the other of which is a steel alloy containingapproximately forty-two per cent nickel.

18. A heat-responsive device comprising a nickel alloy containing aproximatel 42 per cent nickel and a meta 1c element havmg a widelydifferent coeflicient of expansion within the range 200 to 350 C.

19. A heat-responsive device comprising a steel alloy containinapproximately 40 to 45 per cent nickel anil an element having widelydifi'erent coeflicient of expansion at approximately'300 C.

20. A heat-responsive device com rising metallic elements having widelydifferent coeflicients of expansion at temperatures above 200 C., bothelements containing nickel and the nickel content of the element havingthe lower coeflicient at such tempera.- tures being at leastapproximately 40 per cent.

LAURENCE K.

